Mesothelioma Aid

Cooper, Hart, Leggiero & Whitehead

Tomography Applications in Cancer Diagnosis, Prognosis, Treatment,
and Research

Tomography is a term derived from the Greek words tomos, which
is defined as a section or slice, and graphien, which means to measure
or write. While tomography is widely used to advance scientific
disciplines such as archeology, oceanography, astrophysics, materials
science, and others, the utilization of tomography is best known
for Medical Imaging
(MI) applications that are today indispensable to cancer physicians
and researchers alike. MI tomography joins in the battle against
cancer by providing three-dimensional views of internal anatomical
structures such as bone and internal organ tissues.

Cancer can present itself in many different forms in myriad parts
of the body, and prior to the advent of advanced MI technologies,
physicians were extremely limited in their ability to detect many
types of cancer without the use of highly invasive exploratory surgeries.
Today, having to physically enter the body in order to examine anatomical
structures is virtually unheard of due to the countess advances
in MI, nearly all of which rely on tomographic images of one type
or another.

While the initial diagnosis, ongoing prognosis, and therapeutic
treatment of cancer are all areas that have been significantly advanced
through tomographic imaging, so, too, have cancer researchers benefited
from the technology. Very high resolution, color enhanced, and three-dimensional
views of cancer are now invaluable bench and clinical research tools—bringing
cancer into ultra-clear focus is a significant step towards an eventual
cure for the deadly disease.

Basic X-ray Tomography

X-rays have provided physicians with internal views of the human
body since the late 1800’s. First discovered by the German
physicist Wilhelm Roentgen in 1895, X-rays are similar to visible
light rays—both are electromagnetic forms of energy that are
carried by particles known as photons. The chief difference between
X-rays and light rays is the energy levels within the ray’s
respective photons, a variation that is generally expressed through
the precise scientific measurement of wavelengths.

The earliest use of X-rays produced two-dimensional, black and
white images of skeletal structures, as well as views of denser
tissues such as those that make up the lungs. While the ability
to produce basic X-ray images has been hailed as one of the greatest
scientific discoveries in all of human history, when used in concert
with tomographic technologies, X-ray-based MI is elevated to new
heights. In basic X-ray tomography, radiologists and other clinical
personnel create a sectional image of anatomical structures by moving
an X-ray source and image capturing film in opposite directions
during an exposure, and as a result, structures in the focal plane
are viewed in high resolution while all others are blurred. MI technicians
are able to utilize subtle or distinct variations in the movement
of the X-ray source and film to designate specific focal planes
that concentrate on the anatomical structure of clinical interest.

First developed by the radiologist, Alessandro Vellabona, in the
1930s, basic X-ray tomography was designed to overcome the superimposition
of anatomical structures in conventional projection radiography.
The medical images produced through the use of basic X-ray tomography
have proven to be invaluable to oncologists who first need to confirm
the presence of cancer before deciding on appropriate treatments
for the disease. Today, numerous and highly advanced variations
of tomography are possible through the application of tomographic
reconstruction algorithms that work in concert with a computer.

Computed Tomography

Computed tomography (CT) was originally referred to as an EMI scan
because the technology was first developed at a research department
of EMI, a company that is now widely recognized as a leader in the
music and recording industry. Today, CT technology is more commonly
referred to as computed axial tomography (CAT or CT scan). CT creates
high resolution, three-dimensional medical images of the interior
of a solid object through the utilization of an extensive series
of standard, two-dimensional X-ray images that are captured around
a single axis of rotation. This large body of X-ray data is subsequently
manipulated through a process known as windowing, which identifies
specific anatomical structures based on the object’s ability
to resist or block an X-ray beam.

CAT scan machines are very large, circular shaped devices that
can cost between $1-2 million, and as a result of this very high
price tag, the devices are usually found in major hospitals and
cancer centers. Operated by Certified CT Technicians and specially
trained physicians, CAT scan machines provide a painless MI examination
that requires no use of patient anesthesia or sedation. Additionally,
no unpleasant physical side-effects during or subsequent to a CAT
scan are known to exist.

During a CAT examination, the patient will lie on a flat table
that is moved—in extremely precise increments—further
into the circular opening of the machine as an X-ray source revolves
around the patient. During this rotation of the X-ray beam, extremely
thin, sectioned anatomical images are recorded. Once the extensive
collection of sliced images has been compiled, computed algorithms
translate the data into the three-dimensional images that provide
cancer doctors with precise and highly detailed views of any malignant
disease that may be present.

Two additional applications of computed tomography that are widely
used in the detection, prognosis, and treatment of cancer are:

Positron Emission Tomography (PET): A unique tomographic technology
that is highly prized for its ability to image the metabolic function
of cancer. PET scans can locate a tumor while simultaneously determining
if the growth is malignant or benign. Additionally, the effectiveness
of specific cancer therapies can also be judged through the prognostic
use of PET.

Single Photon Emission Computed Tomography (SPECT): Tomographic
imaging widely used in the search for cancer in skeletal structures
(bone cancer). SPECT imaging relies on the use of radioactive
isotopes that are injected into the body and later detected in
specific skeletal sites that are suspected of involvement with
malignant disease.